Hi folks, this is my first post on this forum so I'll try to make it a worthwhile one!
Clapham Junction has a lot of experience over the last few years of crowd management, and has gone to Exit Only quite a few times during various service disruptions (the flooding in June was a particularly mad one). There are several pinch points around the station, mostly in the subway, but usually after 5 or 10 minutes the passenger flow is free enough to allow entrance again.
When the Tube is on strike there are many more people who use CLJ as an alternative, mostly heading towards platforms 1 & 2. As alluded to in earlier posts, the Overground provides an alternative to West Brompton, Kensington Olympia, Shepherds Bush, Willesden Junction (for Euston), Camden, Highbury and Islington, and Stratford, all via the West/North London Line, whilst services from platform 2 serve Shoreditch for the City via Canada Water and Whitechapel. Normally the Southern services from 16 and 17 supplement those trains on the WLL but are not advertised - this allows staff to locally control passenger flows, usually moving some of the back of the queue from the overbridge down to 16 or 17 as appropriate to relieve some of the pressure on platform 1. Those Southern services did not run due to the ongoing Southern issues, so everyone will have joined the line for the Overground with no other alternative.
Whereas normally the other pinch points for crowds building up tend to dissipate within a few minutes (as trains come and go), it would appear from photos that there were just too many crowds in too many places and this didn't happen, and so a decision was made to close the station. I suspect that the subway won't have cleared as quickly as usual if the trains from Wimbledon were so full that people couldn't board, whilst the overbridge was already full of people waiting for the Overground thereby (despite the crowd control barriers) blocking the paths of interchanging people arriving on 3 & 4. Operationally, closing the station is really unusual as the best way to move people on is by getting them on trains as soon as they can get on the platforms, but once the platforms are full to the point of people standing on the edges, there is really no other option left than to temporarily shut the whole thing down.
With circa 30 million entries and exits a year and circa 30 million interchanges a year (a ratio that no other station matches) it is not really a surprise that simply going Exit Only doesn't always solve the overcrowding issues. But with regard to the question "Is Clapham Junction on a normal day a disaster waiting to happen?" the answer is no - it's a busy place but there are plenty of measures in place to keep it flowing as best as possible and keep it as safe as possible for all who travel through there.
By contrast, the evening peak was very quiet apart from a couple of incidents on the SWT side - but the evening peak is always a 'softer' event than the morning i.e. everyone wants to be in the office for 9am, but afterwards they all gradually go home at different times and (if arriving from the Overground on platforms 1 & 2) dissipate across the whole station for their trains home rather than joining a line for one platform.
I hope these thoughts help explain a little bit about the workings of CLJ during disruption...
ThePhantomPhish
